A sieve of this type is known, for example, from German printed application No. 2,634,934. In an effort to combine a filtering or drainage area of large relative cross-section with structural stability of the carrier plate, that known sieve has a number of parallel throughgoing slots--extending over substantially the full length of width of the plate--alternating with rows of shorter slots interrupted by solid portions of the plate surface. Our copending application Ser. No. 317,381 now abandoned, whose disclosure is incorporated by reference into the present one, describes and shows a similar sieve element with either partly or fully throughgoing slots separated by ribs whose lower portions are interconnected by crossbars of different height.
Care must be taken in such sieves that solid particles of the mass being filtered or dewatered do not penetrate into the slots and deform the ribs bounding same, especially when the plate spanning the frame is made of elastic or otherwise yieldable material such as polyurethane, for example. Aside from a possible clogging of the slots by particles wedged therein, the resulting local widening thereof impairs the utility of the sieve as a means for the classification of comminuted solids, i.e. for separating particles with sizes above and below a certain threshold from one another.